1. Field of the Present Invention
The present invention relates to a packet relay device that provides a closed network on a group-by-group basis by virtually grouping a plurality of terminals connected to a network.
2. Description of the Related Art
IP (Internet Protocol) networks have spread over the recent years, and a variety of apparatuses are connected to the network. Along with this circumstance, such a configuration is considered that, e.g., electrical appliances each having a communication function are connected to the network and controlled from a personal computer (which will hereinafter be abbreviated to PC) connected to the same network.
With the spread of this type of network, the number of the apparatuses connected to the network naturally increases, and therefore it is desirable to manage the respective apparatuses in a unified manner. A management method takes, it is considered, such a scheme that, e.g., the individual apparatuses are grouped on an arbitrary unit, and the apparatuses belonging to the group can perform the communications with each other on the group-by-group basis. This scheme enables a search range to be narrowed down by, in the case of searching for a certain terminal, searching the terminal within the predetermined group, and enables a throughput and a period of time needed for the search to be reduced. Further, the security can be ensured by distinguishing between the group belonging terminal and a non-belonging terminal and by restricting an access from outside to the members belonging to the predetermined group.
Thus, in the case of grouping the communication partner terminals dispersing over the network, the terminals individually authenticate the communication partner terminals and ensure the security on a communication route.
On the other hand, as the number of the terminals connected to the network rises, communication services provided from on the network are diversified. For instance, in the case of considering an IP telephony call service, this service includes, in addition to, of course, a one-to-one call service, one-to-many or many-to-many group conference telephony. This type of communication service entails realizing one-to-many or many-to-many communications between the terminals without being limited to only the one-to-one communications. In the one-to-many or many-to-many communications, a communication method such as broadcast communications or multicast communications be, it is required, employed for more efficiently forwarding a communication packet.
Proposed as a method of forwarding a multicast packet and a broadcast packet, as concomitants of performing the multicast/broadcast communications, to other networks are a method (termed a method 1) of converting a multicast packet into a unicast packet and thus forwarding the packet and a method (termed a method 2) of translating an IP address of the broadcast packet into an IP address of the broadcast packet of a destination.
The conventional method utilizing the multicast involves setting a router for routing the multicast packet within a core network in the communications via the Internet and the large-scale core network. This scheme, as well as causing a rise in load on management of the multicast addresses, leads to a heavy load on the routing process in each relay device.
Further, the method 1 needs to manage, because of translating the multicast packet into the unicast packet and forwarding the packet, for realizing the many-to-many communications, all pieces of address information about the destination terminal in the communications, to which the packet should be forwarded, resulting in a loss of merit of the multicast communications. Furthermore, the method 2, by which the predetermined relay device translates an address of the broadcast packet into a broadcast address for another network, therefore remains unchanged with the unicast communications in the multipoint-to-multipoint communications.
Namely, those methods are incapable of improving scalability as the number of the terminals connected to the network rises and actualizing forwarding the multicast packet/broadcast packet on a predetermined management basis (group-by-group basis). It should be noted that technologies disclosed in the following documents are given as the conventional arts related to the invention of the present application. The Patent document 1 is a Japanese Patent Application Laid-Open Publication No. 2001-230774. The Patent document 2 is a Japanese Patent Application Laid-Open Publication No. 2004-282199.